Weathering

Physical weathering

water

wind

wind

Heat

Freezing

Chemical weathering

Chemical weathering is the process by which rocks are decomposed, dissolved or loosened by chemical processes to form

smaller materials.

• Rainwater reacts with elements in the air to make an acid that eats away at the surface of rock. This makes it softer and more open to physical weathering. Acid rain caused by pollution in the atmosphere increases chemical weathering.

Biological weathering

There are two main types: mechanical and chemical. Biological weathering isn't really a process, but living organisms can

cause both mechanical and chemical weathering to occur.

• Plants grow in the crevices of rocks, creating a wedge. Their roots travel deeper into the crevice as they search for water. As the roots grow thicker, they make these cracks bigger.

• Burrowing animals also increase the size of the crevices in rock. This allows water to penetrate deeper into the rock where it can freeze and expand.